Large quantities of waste matter, waste oils, sludges, and the like are discharged from production factories of various industrial plants as is well known in the prior art. Disposal of these wastes has become a very important measure to be taken against environmental pollution which unavoidably occurs with the development of industry. As to the disposal of highly viscous fluids such as muddy slurries and sludges and the like, technology has been widely employed which provides solid-liquid separation and which disposes of the resulting solid matter by incineration and reclamation, reutilizing the liquid in an appropriate way. Various pressure-feed devices having large-capacity, high-output and high-durability disposing capacities have been used for such disposal purposes.
A pressure-feed apparatus 1 of this kind which has been widely used is shown for example in FIG. 3 of the accompanying drawings. An hydraulic fluid, e.g. oil 5, is supplied by an oil pressure generation apparatus 4 to an elastic film or tube 3 which is stored in a drum-shaped casing 2 and which can be made of a rubber material. The flexible film or tube 3 is pressurized from inside for expansion and contraction in a cyclical operation so that a solution 6 to be disposed, such as a slurry, is sucked from a slurry tank 7 into the casing 2 and is pressure-fed to a processing apparatus 8 of the next stage such as a filter press.
The solid component of the slurry 6 is taken out as a cake by predetermined solid-liquid separation treatment while the liquid component is clarified and is discharged appropriately or reutilized effectively.
If the solution to be disposed is a waste liquid containing chemical agents and/or microorganisms, however, fermentation may occur in the solution if it is stored in the tank for long periods and bubbles come to be mixed in the solution. If the solution to be disposed of is highly viscous, natural deaeration becomes very difficult. If the pressure-feed operation of such a solution is carried out by use of the pressure-feed apparatus 1 described above, the bubbles 10, 10, . . . mix during the suction process because the inside of the casing 2 is closed or opened by a check valve 9 interposed between the casing 2 and the slurry tank 7. Since the bubbles 10, 10 . . . are compressible, they gather and stay inside the casing and cavities are formed locally. Accordingly, even when the elastic film 3 effects a sufficient expansion/contraction operation, the capacity of these cavities changes and the pressure is not transmitted effectively, thereby causing so-called "damping". For this reason, the slurry solution 6 cannot be discharged completely from inside the casing 2 to the processing apparatus 8 of the next stage.
Even if the casing 2 is installed in a vertical arrangement to position suction and discharge ports atop, natural suction of the slurry 6 occurs sometimes. If the slurry 6 is highly viscous, the bubbles 10 are ruptured at the time of suction and a substantial suction quantity of the slurry 6 into the casing 2 becomes insufficient, so that a smooth feed/drain operation of the pressure-feed apparatus 1 cannot be made.
As compression inside the casing 2 is repeated by the operation of the pressure-feed apparatus 1, the temperature of the staying bubbles 10 rises. The rising temperature causes the problem of the pressure-feed apparatus 1 reaching a high temperature such that packings and the like interposed in the connection portions of pipings become fatigued and/or their service life is reduced.
For the reasons described above, in a so-called "plunger type" pressure-feed apparatus, the solutions to be disposed are limited to those which do not contain modifying materials or bubbles, and the pressure-feed apparatus cannot dispose of all kinds of waste liquids including highly viscous liquids.
Because the slurry 6 is sucked and discharged between the elastic film 3 and the casing 2 outside the elastic film 3, the highly viscous liquid cannot be sucked efficiently by the negative pressure in the contraction process of the elastic film 3 at the time of suction. Another problem is the occurrence of folding of the elastic film 3 which is likely to cause its own fatigue.